<!DOCTYPE html>
<html lang="en">
<head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>go2rtc - WebTorrent</title>
    <style>
        body {
            background-color: black;
            margin: 0;
            padding: 0;
        }

        html, body, video {
            height: 100%;
            width: 100%;
        }

        div {
            position: absolute;
            top: 50%;
            left: 50%;
            display: flex;
            flex-direction: column;
            transform: translateX(-50%) translateY(-50%);
        }
    </style>
</head>
<body>
<video id="video" autoplay controls playsinline muted></video>
<div id="login">
    <input id="share" type="text" placeholder="share">
    <input id="pwd" type="text" placeholder="password">
    <button id="connect">connect</button>
</div>
<script>
    async function PeerConnection(media) {
        const pc = new RTCPeerConnection({
            iceServers: [{urls: 'stun:stun.l.google.com:19302'}]
        })

        const localTracks = []

        if (/camera|microphone/.test(media)) {
            const tracks = await getMediaTracks('user', {
                video: media.indexOf('camera') >= 0,
                audio: media.indexOf('microphone') >= 0,
            })
            tracks.forEach(track => {
                pc.addTransceiver(track, {direction: 'sendonly'})
                if (track.kind === 'video') localTracks.push(track)
            })
        }

        if (media.indexOf('display') >= 0) {
            const tracks = await getMediaTracks('display', {
                video: true,
                audio: media.indexOf('speaker') >= 0,
            })
            tracks.forEach(track => {
                pc.addTransceiver(track, {direction: 'sendonly'})
                if (track.kind === 'video') localTracks.push(track)
            })
        }

        if (/video|audio/.test(media)) {
            const tracks = ['video', 'audio']
                .filter(kind => media.indexOf(kind) >= 0)
                .map(kind => pc.addTransceiver(kind, {direction: 'recvonly'}).receiver.track)
            localTracks.push(...tracks)
        }

        document.getElementById('video').srcObject = new MediaStream(localTracks)

        return pc
    }

    async function getMediaTracks(media, constraints) {
        try {
            const stream = media === 'user'
                ? await navigator.mediaDevices.getUserMedia(constraints)
                : await navigator.mediaDevices.getDisplayMedia(constraints)
            return stream.getTracks()
        } catch (e) {
            console.warn(e)
            return []
        }
    }

    function getOffer(pc, timeout) {
        return new Promise((resolve, reject) => {
            pc.addEventListener('icegatheringstatechange', () => {
                if (pc.iceGatheringState === 'complete') resolve(pc.localDescription.sdp)
            })

            pc.createOffer().then(offer => pc.setLocalDescription(offer))

            setTimeout(() => resolve(pc.localDescription.sdp), timeout || 5000)
        })
    }
</script>
<script>
    function decode(buffer) {
        return String.fromCharCode(...new Uint8Array(buffer))
    }

    function encode(string) {
        return Uint8Array.from(string, c => c.charCodeAt(0))
    }

    async function cipher(share, pwd) {
        const hash = await crypto.subtle.digest('SHA-256', encode(share))
        const nonce = (Date.now() * 1000000).toString(36)

        const ivData = await crypto.subtle.digest('SHA-256', encode(share + ':' + nonce))
        const keyData = await crypto.subtle.digest('SHA-256', encode(nonce + ':' + pwd))
        const key = await crypto.subtle.importKey(
            'raw', keyData, {name: 'AES-GCM'}, false, ['encrypt', 'decrypt'],
        )

        return {
            hash: btoa(decode(hash)),
            nonce: nonce,
            encrypt: async function (plaintext) {
                const cryptotext = await crypto.subtle.encrypt(
                    {name: 'AES-GCM', iv: ivData.slice(0, 12), additionalData: encode(nonce)},
                    key, encode(plaintext),
                )
                return btoa(decode(cryptotext))
            },
            decrypt: async function (cryptotext) {
                const plaintext = await crypto.subtle.decrypt(
                    {name: 'AES-GCM', iv: ivData.slice(0, 12), additionalData: encode(nonce)},
                    key, encode(atob(cryptotext)),
                )
                return decode(plaintext)
            }
        }
    }
</script>
<script>
    async function connect(share, pwd, media, tracker) {
        const crypto = await cipher(share, pwd)
        const pc = await PeerConnection(media || 'video+audio')
        const offer = await crypto.encrypt(await getOffer(pc))

        const ws = new WebSocket(tracker || 'wss://tracker.openwebtorrent.com/')
        ws.addEventListener('open', () => {
            ws.send(JSON.stringify({
                action: 'announce',
                info_hash: crypto.hash,
                peer_id: Math.random().toString(36).substring(2),
                offers: [{
                    offer_id: crypto.nonce,
                    offer: {type: 'offer', sdp: offer},
                }],
                numwant: 1,
            }))
        })

        ws.addEventListener('message', async (ev) => {
            const msg = JSON.parse(ev.data)
            if (!msg.answer) return

            const answer = await crypto.decrypt(msg.answer.sdp)
            await pc.setRemoteDescription({type: 'answer', sdp: answer})

            ws.close()
        })
    }

    document.getElementById('connect').addEventListener('click', () => {
        const share = document.getElementById('share').value
        const pwd = document.getElementById('pwd').value
        connect(share, pwd)
        document.getElementById('login').style.display = 'none'
    })

    if (location.hash) {
        const params = new URLSearchParams(location.hash.substring(1))
        const share = params.get('share')
        const pwd = params.get('pwd')
        const media = params.get('media')
        const tracker = params.get('tr')
        connect(share, pwd, media, tracker)
        document.getElementById('login').style.display = 'none'
    }
</script>
</body>
</html>